Telephone system



July 2, 1935. w B, STRICKLER 2,006,489

TELEPHONE SYSTEM Filed Oct. 12, 1953 5 Sheets-Sheet l IN VEN TOR WBSTR/C/(L ER A TTORNE V July 2, 1935.

W. B. STRICKLER TELEPHONE SY-STEM Filed Oct. 12, 1953 3 Sheets-Sheet 2 F/G.Z

REGISTER TO GROUP INVENTOR W B.$7'R/CKLER A TTORNE V system.

more stares ATENT oFrIcEY TELEPHONE SYSTEM Walter B. S trickler, East Orange, N. J.,jassignor to Bell Telephone Laboratories,"Incorporated,

New York, N. Y., a corporation of New York Application October 12, 1933," Serial Not 693,277 f 11 Claims. (01. 119-41 This inventionrelates to telephone exchange systems and more particularly to trunking systems where A and B operators are employed in trunking calls between oliices of the exchange In such systems it is customary for the Atopcrators in originating ofiices to receive the calls from calling subscribers linesterminating therein and to extend them over trunks to the an A operator selects an idle trunk in agroup of trunks terminating at the BV operators position'of a terminating ofiice the trunk is automatically associated with the B operators position equipment if the fB operators position is occupied and free, and the B operator is apprised of the waiting call by a tone signal applied to her position telephone set and by a flashing lamp signal associated with the particular calling trunk which'has been associated with the position equipment. No talking connection is, however, established between the originating A operators telephone set and the B operators telephone set until after the B operator in response to the tone signal depresses her position listening key. When the listening key hasbeen operated the tone signal is first discontinued, order tones are then transmitted in the wellknown manner to apprise the A operator that she may pass to the B operator the information for completing the desired call and then following the termination of the order-tones the B operators telephone set is connected in to a talking connection with the A operators telephone set.

To disconnect the trunk from the B operators position equipment the B operator may either plug the trunk up into the jack of the called line, the number of which has been passed to the B operator, or by again depressing the position listening key. If calls are simultaneously waiting on more than one trunk incoming to the B operators position the first depression of the position listening key will listen'the B operator in on a first calling trunk and a subsequent depression or the listening key will cause the disassociation of the B operators position equipment from the first trunk and the listening in of the B? operator on another calling trunk.

While the invention has beendisclosed as applied to the trunking of calls from an A operators position toa B operators position, it is to be understood that it is equally applicable to all trunking systems in which it is necessary to trunl: calls from one operators position to another ope erators position.

For a clearer understanding of r the invention reference may be had tothe-following detailed description taken in'connection with the accompanying drawings in which; I

Fig. 1 shows a calling line terminating in an originating ,ofiice of an exchange system, the outgoing ends of two of the trunks extending to a terminating ofiice .ofthe exchange and an A operators cord circuit by, means of which the calling line may be connected to any of said trunks.

Fig.2 shows the incoming ends of the trunks terminatingxin plugs ataB operators position in a terminating OfilCG anda called subscribers line.-. 1

Fig. '3 shows the position equipment at the B operators position common to alltrunks incoming to the position. 1 I

Tocompletely "illustrate thejinvention Fig. 2 should beplacedat the right of Fig. land Fig. 3 should be placed beneath Fig. 2 with. the conductors extending to the margins of the respective figures in alignment.

Itrwill be assumed that; the calling subscriber at substation I initiates a call by removing his receiver. from the switchhook thereby operating line relay IM and lighting the linelamp I02. The A operator, oneof whose cord circuits is shown at I03; seeing the lightedlamp I02 inserts the answering plug I04 of the cord circuit in the line jack I05 thereby operating the cut-olf relay I06 toextinguish the lamp I02, and throws the 1is-' tening. key I01 to connect her telephone. set (not shown) with the cord circuit. The operator is now enabled to converse with the calling sub scriber'andtoobtain. from him the number of the desired line. 1

It will further be'assumed that the calling subscriber desires a connection with the line whose substation is shown at 200 and which terminates in another office of the exchange; The A operator will therefore testfor an idle trunk of the group of trunks extending to the ofiice in which the desired line terminates and, for example, finding the trunk I20 of the group idle will insert the calling plug,l08.of cord circuit I03 into the. jack I09 of .thisytrunkrrflhe called super-=- visory lamp lI0 will therefore become lighted in an obvious circuit over the sleeves of plug I08 and jack I00 and a circuit will also be established from battery through the lower right winding of repeating coil III, winding of supervisory relay IIZ, rings of plug I08 and jack I00, the lower left winding of repeating coil I I3, both high and low resistance windings of trunk relay I I4, upper left winding of repeating coil II3, tips of jack I 09 and plug I08, upper right winding of repeat ing coil III to ground. Relay H4 operatesin this circuit but since the lower high resistance winding of relay IN is included in the circuit of supervisory relay II2, relay II2 does not operate at this time and consequently supervisorylamp I I0 remains lighted. 1

With relay I I4 operated a circuit is established from ground at its contact-over conductor II5,

' the upper back contact of relay I to battery through the lower winding of relay 202. Relay 202 operates andat its inner upper front contact establishes a circuit extending from battery through the lower winding of relay 20I thence in parallel through resistance 203- and the upper winding of relay 202, inner upper front contact of relay 202, lower back contact and lower winding 'of sleeve relay 204, to ground on conductor H5. 'Relay 20I operates and relay- 202 is held operated over this circuit, but relay 204 does not operate. Relay 20I upon operating now looks over its upper winding'and inner front contact directly to ground on conductor H5, and at its inner upper back contact opens the initial operating circuit of relay 202. With relays MI. and 202' both operated, the trunk guard lamp 205 is lighted in a circuit extending from battery through lamp 205, upper front contact of relay 20I,'upper front contact of relay 202, to ground through resistance 206.

At its lower front contact, relay 202 establishes a' circuit extending from ground through the winding of start relay 201, thence if nocall exists on succeeding trunks of the group over back contacts in series of relays of I such succeeding trunks corresponding to relay 208-to battery. Relay 201 upon operating establishes'a circuit for relay 20!! extending from battery through the winding of relay 208, upper alternate contacts of start relay 201, normal contacts 'of' relay 201' of the next preceding trunk, if such trunk is not in a calling condition, winding of relay 209 to ground'at the back contact of relay 2I0. In the case illustrated trunk I30 to-which relay- 201 is individual is the first trunkin the group and trunk I20 to which the A operator has connected is the second trunk in the group. Relay 208 operates supplying locking ground for itself and for the operated relay 208 and operating ground for relay 2 I 0 which operates removing the initial 'op-. erating ground for relays 208 and'209.

With relays 201 and 208 both operated, the tip talking conductor I2I of trunk I20 is extended over the inner lower front contact of relay 201 and the inner upper front contact of relay 208 to conductor 2H extending to the B operators position circuit and the ring talking-conductor 122 is extended over the lower front contact of relay'208 to conductor 2I2, extending the B operators position circuit. Since relay 201 upon operating opens its upper normal contacts the chain circuit extending from ground at the contacts of relays 209 and 2I0 is opened and it is not possible for the relay corresponding to relay 208 of a succeeding trunk to become operated at this time. Also since relay 208 .upon operating has opened its upper back contact, it is not possible for the relays corresponding to relay 201 of the preceding trunk, in this case relay 201' of the first trunk I30, to become operated. Thus the talking conductors of no other trunks can be connected to conductors 2i I and 2I2 while relays 201 and 208 remain operated and therefore only one talking connection can be established from the A operators position to the B operators position at one time.

If the B operators headset 300 is not at this time plugged up, relay (MI is operated over the lower back contact of relay 302 and a circuit is established from ground, resistance 206, upper contacts of relays 202 and 23 I middle lower front contact of relay 283, conductor 2I3, winding of pilot relay 2M, conductor 2i5, contact of relay 30I, back contact of relay 303, winding of relay 334 to battery. Relay 304 operates in this circuit operating slow to operate relay 305 which in turn operates slow to operate relay 30%. Relay 3% upon operating connects direct battery to the operating circuit of relay 30 1 thereby shunting the guard lamp 203 to cause it to become extinguished and shunting relay 394 which releases in turn releasing relays 305 and 30S. Relay 306 upon releasing removes shunting battery from the guard lamp 235 and from relay 394. The lamp now relights and relay 304 reoperates. This cycle of operations is repeated whereby lamp 205 intermittently flashes as a signal that there is a call awaiting the attention of the operator.

If the B operators headset 309 was plugged up at the time a call was incoming on one of the trunks of her position, or the operator plugs up her headset upon seeing the flashing of the guard lamp of the calling trunk, a circuit is established from ground through the right winding of repeating coil 381, tips of jack 308 and plug 300, headset transmitter 3 I0, tips of plug 3 I I and jack 3I2 to battery through the Winding of relay 3I3. With relay 3I3 operated an obvious circuit is established for relay SE12 which opens the operating circuit of relay 3% to stop the flashing of the guard lamp of the calling'trunk. A circuit is now established from battery through the lower winding and lower front contact of relay RSI, lower front contact of relay 201, inner lower front contact of relay conductor 22I, lower front contact of relay 362, inner right back contact of relay 335, winding of relay 336 to ground at the outer left back contact of relay Bic. Relay operates in this circuit closing at its contacts a locking circuit for itself independent of relay 35G. A circuit is also established for relay 3M tending from ground through the winding of this relay, inner lower front contact of relay 302, conductor 2I2, thence as traced to conductor winding of trunk supervisory relay Ht, lower right winding of repeating coil I I3 to battery and ground. Relay 3M operates in this circuit, due to the high resistance of its winding, the trunk supervisory relay I 56 does not operate. R.-- lay-3l4 upon operating establishes a circuit extending from ground at the right normal contacts of relay 3I5, contacts of relay 3M, inner right normal contacts of relay 3I6 to battery through the right winding of relay 3!? and in parallel therewith over the back contact of relay 3I8 to battery through the winding of relay 5H9.

Relays 3H and 3i9 both operate, relay 3!!! upon operating establishes a circuit from battery, interrupter 320 through the primary winding of tone coil 32I to ground at the inner lower front contact of relay 3!?! and connects the secondary winding of tone 001132! in a circuit extending from the lower terminal of the secondary winding, next to inner lower front contact of relay 3 l9, condenser 322, left windings of repeating coil 301, upper front contact of relay "319 tothe upper terminal of the secondary winding of tone coil 32!; Tom current set up in this circuit by the interruptions of current in the primary winding of the tone coil 32!, now reach the operators headset receiver 323, over the sleeves of jack 3!2 and plug 3! I, and sleeves ofjack 338 and plug 309 and the operator is given asteady'warning tone that a'call is awaiting'her attention; 1

Hearing the steadytone; the operator depresses the non-locking positional listening key 324, thereby establishing a circuit from ground at the key over the upper front. contact of relay 302; back contact of relay. 325, to battery through the winding of relay 3!8.- Relay 3! operates locking itself through the windingof relay 325 and its own upper front contact to'ground at the right front contact of relay 3 i and openingthe circuit of relay 319 which now releases. Relay 3!!! upon releasing. opens the primary and secondary cir-- cults of tone coil 32! to discontinue the. applica tion of steady tone to the-operators headset receiver and closes acircui'tirombattery, winding of relay 326, lower back contact of relay'3l9, lower L front contact of relay 3l3;-thence as traced-to ground at the rightjnormal contacts of relay 3E5. Atits inner lowerfront contact relay 325 reestab lishesxa circuit through the primary winding of tone coil 32! thence over the right normal contacts ofrelay 321 to ground at the lower normal contacts of relay 328,- and establishes a circuit fromthe lower terminal of the secondary winding' of'tone coil 32!, next to the lower'front contact of-relay 326, lower back contact of relay 329, condenser 330, inner lower front contact'of relay 302, thence as traced to trunk conductor I22 through the right'windings of repeating coil I I3, returning over trunk conductor I2 I, thence as traced over conductor 2i i, inner upper front contact of relay 382, upper back contact of relay 329, upper front contact of relay 326 to the upper terminal of the secondary winding of tone coil- Tone current induced into, this circuit from the primary winding of tone coil 32! is induced into the left windings of repeating coil i !3 and reaches the A operators telephone set. Relay 323 also closes a circuit for slow to, operate relay 32! extending from ground, inner upper front contact of relay 326; middle'lower normal contacts of relay 329 to battery through the winding of slow-to operate relay 321. Relay 32l operates after an interval opening at its right normal, contacts the previously traced circuit through the primary winding of tone coil 32! to discontinue the generation and transmissionof tone current to the A operators telephone set and at its left front contactextends the circuit over which it wasoperated to the winding of slow to operate relay 333. After an interval relay 33!) operates and the primary winding of tone coil 32! is then reestablished as previously traced over the innerlower front contact of relay 326 thence over the right alternate contacts of relay 32'! and the left contacts of relay 333 to ground at the lower normal contacts of relay 328. A second impulse of tone current is now transmitted over the previously traced circuit to the -A operators telephone set. Relay 33!! upon operating also closes over its'right con-tact an obvious circuit for slow'to'operate relay 328 which after an interval opens at its lower normal contacts the previously traced circuit through the primary winding of tone coil 32! to discontinue the generationand transmission of tone current. Two: impulses of tone current'have now been transmitted to the A operators telephone set as a signal that she may proceed to transfer information for the completion ofthe desired connection to the B operator.

it During the transmission of these tone signals, the

B operator also may hear the tone signals over a branch circuit extending from ground through the left winding of repeating coil'33 I, condensers 332 and 333, the upper back contact of relay 328, and the upper back contact of relay 3!9, and the inductive connection to the B operators headset receiver 3!!) over the right winding of repeating coil 33!.

Relay 328 upon operating also opens this branch tone circuit and closes an obvious circuit for relay 329 whichat its middle lower transfer contacts opens the operating circuit of relays 32! and 333 and establishes a holding circuit for relay'323 for' maintaining this relay operated under the control of relay 326 after relay 330 releases. Relay 329 at its outer back contacts also disconnects the secondary winding of tone coil 32! from the talking circuit extending to the A operators position and connects this talking circuit over its outer front contacts to 'the B operators headset receiver. The B operator is now listened in on the calling trunk and may receive instructions from the A operator for extending the connection.

n A V Relay 329 upon operating also closes an operating circuit for relay 313 extending from battery, inner lower front, contact of relay 329, winding and left normal contacts of relay 3l6 to ground at the contacts. ofrelay 336. Relay 3l6 upon operating locks to ground at its inner left front contact, opening at its outer left back contact the initial operating circuit of relay 333, transferring at its inner right contacts the operating circuitsof relays 3!! and 326 from ground at the normal contacts of relay 3l5-over the front tact of relay 3M, to ground at the'contacts of relay 336, and at its outer right front contact closing an obvious circuit for relay 3! 5. Relay 3 5 now operates to'prepare the circuit of pegcount meter 331 and to prepare locking circuits for relays 303 and 335.

When the operator releases the listening key .324, relay 325 operates in the locking circuit of 325, the left back contact of relay 334 to the right I winding of relay 335 preparatory to the release of the operated position equipment. e

The B operator having received the necessary information from the A operator proceeds to complete the desired connection. She first tests the-desired line to determine its idle or busy condition by touching the tip of the trunk plug 2!6 to the sleeve of the line jack 2. If the line is busy. she will receive a click in. her headset receiver through the windings of repeating coil 33! over a circuit extending from battery on the sleeve of jack 2H, tip of plug 2!6, upper back contact of relay 234, conductor! !8, middle upper front contact of relay 302, condenser 332, to

ground through the left winding of "coil 33!.

through the cut-off relay 2I9, sleeves of jack 2I1 and plug 2l6, upper winding of sleeve relay 204 to battery through the lamp 205. Relays 2I9 and 204 operate in this circuit, relay 2I9 disconnecting the line relay 220in the usual manner. 1 Relay 204 upon operating opens at its upper. back contact the connection between the tip of plug I and 208 upon releasing in turn release relay 336..

The release of relay 336 in turn releases relays 326, 328, 329, 3I5, (H6 and SH. Relay- 3I5 being slow to release closes a circuit from ground at the right back contact of relay 3| 6, over the left contact of relay 3I5, to the pegcount meter 331 for a sufficient time to operate the meter.

When relay 204 operated as previously described, a circuit was established from battery, winding of ringing relay 222, back contact of relay 223, back contact of ringing trip relay 224, lower front contact of relay 204, upper back contact of relay 202, upper front contact of relay 20 I, upper winding of relay 204, sleeves of plug 2H5 and jack 2I1 to ground through the winding of cut-off relay 2I9. Relay 222' operates in this circuit opening at its back contact the connection between the talking conductors of the trunk and the tip and ring contacts of plug 2I6 and, assuming that the operator has depressed ringing key 225, closing acircuit extending from ground at the right back contact of pick-up relay 226, upper front contact of relay 222, upper front contact of relay 204, tips of plug ZIB and jack 2 I 1, through the substation ringer relay 221, rings of jack 2H and plug 2l6, lower front contact of relay 222, left alternate contacts of key 225, right winding of trip relay 224, to the source of ringing current 228. Relay 221 operates in this circuit closing a circuit for the substation ringer 229, extending from ground through the ringer over the rings of jack 2I1 and plug 2l6, thence as traced to the ringing source 228. The ringer now operates as'long as the key 225 remains depressed. When the called subscriber answers by removing his'receiver from the switchhook, the trip relay 228 operates in the usual manner openingfat its contact the shunt around the winding of relay 223 which now operates in the circuit previously traced through the winding of relay 222. Relay 223 upon operating shunts the winding of ringing relay 222 which now releases to open the previously traced ringing circuit and to close the tip and ring conductors of the trunk through to the called-line. During the application of ringing current to the called line, ringing induction tone was transmitted back over condensers 230 and 231 and trunk conductors I2I and I22 to the calling subscribers line so that the calling subscriber is apprised of the fact that the desired subscriber is being rung.

Upon the release of ringing relay 222, a supervisory circuit is established from the substation of the called line over the back contacts of relay 222, trunk conductors I2I and I22, right :wind ings of'repeating coil 3, and winding of supervisory relay I I6 thereby operating relay I I6. Relay II6'upon operating shunts the lower high resistance winding of relay II 4 thereby decreasing the resistance of the circuit previously traced through the winding of cord supervisory relay II2 to such an extent that relay H2 operates to shunt the supervisory lamp IIO which becomes darkrasa signal to the A operator that the called .2

subscriber has answered.

Upon the termination of the conversation both the calling and called subscribers will return theirrreceivers to their respective. switchhooks. The return of the calling subscribersreceiver to its switchhook opens the circuit of the answering supervisoryrelay I23 which releases to cause the answering supervisory lamp I24 to become lighted. The return of the called subscribers receiver to its switchhook releases the trunk supervisory relay H6 which in turn removes the shunt from the lower winding of relay II4 thereby causing the release ofcord supervisory relay I I2 and the lighting of lamp I I0. TheA operator noting the lighting of both lamps H0 and I24 now takes down the cord-circuitl03 thereby restoring the calling line to its normal non-calling condition and releasing trunk relay II4. Relay II4 upon releasing inturn releases relay 20I which causes the lamp 205 to light as a disconnect signal. When the B operator removes plug 2| 6 from jack 2I1 in response to the lighting of lamp 205, relays 204 and 223 release, and the called line is restored to its normal condition.

If the B operator desires to release her position equipment from the trunk, before she plugs the trunk into the jack of the desired line she may. do so by reoperating the l-rey.324. It will be recalled that after first operating and releasing key 324 to listen in on the trunk, relays 3I8, 325, 326, 328, 329, 3I5, 3I6, 3I1 and 336. are operated. The reoperation of key 324 at this time establishes a circuit from ground at key 324,'front contact of relay 325, left back contact. of relay 334, right winding of relay 335 to battery. Relay 335 upon operating locks in a circuit extending from battery, right winding of relay 303, outer right back contact of relay 334, left winding and contact of relay 335 to ground at the right contacts of relay 3I5. Relay 303 operates in this circuit and locks in a circuit from battery through its left winding and left contact to ground at the right contacts of relay 3I5. Relay 303 also'opens the previously traced circuit over which the guard lamp 205 was flashed'and extends its locking ground through the right winding-of relay 334 to battery and through the left contact and left winding of relay 3" to battery thus operating relay 334 and holding relay 3I1 operated. Relay 334 'upon operating locks under thecontrol of key 324, opens the initial operating circuit of relay 335, opens the initial operating circuit of relay 303' and opens the circuit of relay 33B. Relays 334, 303 and 3" now remain operated under the control of relay 3I5. With relay 334 operated a circuit is closed from ground at the right contacts of relay 3I5, over the contact and low resistance left winding of relay 335, outer right alternate contacts of relay 334, lower front contact of relay 302, conductor 22I,'inner lower front contact of relay 208,'lower front contact of relay 201 to the lower front contact of relay 20I, thus causing relay 202 to release in turn releasing relays 201 and 208. The release of relay 201 opens the circuit just traced through the left winding of relay 335 whereupon relay 335 releases. With relays 231 and 208 both released, the trunk is disconnected from the B position circuit. When the operator again releases key 324,

relay334 releases and if no other call is awaiting The operation of the circuit with more than one call awaiting the attention of the B operator operator has completed the extension of the call incoming over the trunk I20, the A operator or another A operator plugs a cord circuit into the jack I09 of trunk I30 thereby causing the opera tion of relays II4 20I and 202' in the manner previously described in connection with trunk I20. Since however relay 208 of trunk I20 is operated, the operation of relay 202' is ineffective at this .time to operate relay 201' and'consequently relays 201 and 208 do not operate to connect the B operators position circuit with trunk I30. Lamp 205 is however steadily lighted through the operation of relays 20I and 202' as a. trunk guard signal. l-

The B operators position circuit being connected to trunk I20, the B operator receives a .call waiting tone and proceeds to operate key 324 to transmit theorder tones to the A operators position and to listen her in on, the trunk as. previously ..described.. 7 After receiving the necessary informationfrom the A operator, the B operator may release herposition circuit from 'the trunk I20 by again operating the key 324.

It will be recalled that after first operating and releasing key 324 to listen in on the trunk I20, relays 3I8', .325, 326, 320, 329, 3I5, 3I6, 3I'I and 336 are operated. The reoperation of key 324 at this time establishes a circuit from-ground .at key 324, Irontcontactof relay 325, left back contact of re1ay'334, right winding of relay 335, to battery. Relay 335 upon operating locks in a circuit extending from battery, right winding of relay 303, outer right back contact of relay 334, left windin! and Contact of relay 335, to ground at the right contacts of relay 3I5. Relay 303 operates inthis circuit, locking in a circuit from battery through its left winding and left contact to groundat the right contacts of relay 3 I5. Relay 303 also opens the previously traced circuit over which the guard lamp 205 was flashed and extends its locking ground through the right wind ing of relay 334 to battery and through the left contact and left winding of relay 3II tobattery, thus operating relay 334 and holding relay 3I'I operated. Relay 334 p perating locks under control of key 324, opens the initial operating circuit of relay 335, opensthe initial operating circult of relay 303 and opens the circuit of relay 336. Relays334, 303 and 3I'I now remain operated under the control of relay 3I5. With relay 33loperated a circuit is closed from ground at the right contacts of relay 3I5 over the contact and low resistance left winding of relay 335., Outer right alternate contacts of relay 334, lower front contact of .relay 302, conductor 22I, innerlower front contact of relay 208, lower frontucontact of relay 201, through'the lower front contactiof relay v,20I, thus causing relay 202 to release,

turn releasing relays 203i and 200. The release of relay 201 opens the circuit justtraced through the left winding of relay 335 whereupon relay 3,35 releases. With relays 201 and 208 both released, the trunk I20 is disconnected from the B position circuit and relays 201'. and 208 may now operate to connect the trunk I30 to the position circuit.

With trunk I30 connected to the position 'cir cult relay 3I4 which released upon the releas of; relay 208now reoperates in a circuit over {the inner lower front contact of relay 302, conductor 2I2..the lower front contact of relay208f, cone ductor I22, winding of trunk supervisor relay I I6 to, battery and ground throu h the lower right. winding of r p ating coil I I3. In the meantime the operation of relay 334 has released relay 336 which in turn has released relays 326, 328, 329 and M6, Relay 316 in turn p n th circuit of relay 315. Howev r, since relay 3 5 is slow to release, it will not have released. o open at its right alternate contac the. holding circuit of relays 303, and 3]! before relay 3M reoperates. Consequently, relay 3 doesnot re: lease before a circuitis established hereiorfrom. battery through its right winding, inner right normal-oontacts-of relay 3I6, contacts ofrelay 3I4 to-ground at the right normal contacts of relay 3I5and since relay 3!! does-not relea e; it holds. re1ays3l8 and .325 operated. Assoon, however, as relay 3I5 releases, the holding .circult of relay 303 is opened and relay 303releases in turn opening the operating circuit of relay 334 which will not release ifthe operator has not 7 released key. 324. As. soon as key 324 is released,

.relay 303 also releases.

applied to the B operators headset as a call waits ing signal. Since relay 316 is now released the circuit ofrelay-326 is again established from bat: tery, throughits winding, the lower back C0117 tact of relay 3I9, the lower front contact of relay 3I8, the inner right normal contacts of relay '3I6, contacts'of relay 3I4 to ground at the normal contacts of relay 3Ii. Relays 326, 321; 328, 32.9 and 330' then operate in the manner previously described to transmit order tones over the 0011+ nected trunk I30 tothe A operators telephone set and to connect the B operators headset to enable the B operator to receive information from the A operator. This second call is then completed andthe trunk 130- disconnected from the B posi- .tion circuit in the manner just described for the first call, these'operations continuing as long as calls are waiting the attention of the B operator.

What is claimed is: 1

1;.'.In a-telephone exchange system, first ofiices, a second 'ofiice, trunks for trunking callsfrom a first office .to said second office, an operators p0? :sition equipment at said second officerhavinga telephone set and a key, meansoperableupon the seizu'reof a trunk at a first office for associating. said operators position equipment with said trunk, means operable by a first operation of said key for connecting saidtelephone set into a: talking. connection with said first office over said trunk, and means operable by the second opera.- tion of said key for entirely disconnecting .said position equipmentfromsaid trunk. '2. In a telephone exchange system, first ofilces, a secondoifice, trunksfortrunking callsfrom a first office to said second oflloe, an operators-position equipment at said secondoifice, havinga telephone set, a key, and means for transmitting order tones tosaid first office, means'operable upon-the seizure of a trunk at a first office for as s'oci'ating. saidv operators position equipment with for disconnecting said position-equipment from said trunk. r a r 3. In a telephone exchange system, first ofiices, a second oifice, trunks for trunking callsfrom a first ofiice to said second ofiice, an operators position equipment at saidsecond ofiice having a telephone set anda key, means operable upon the seizure of a trunk at a first office for associating said operators position equipment with said trunk, means operative upon the'association of said trunk with said position equipment for transmitting a tone to said operators telephone set as a call waiting signal, means operable by the first operation of said key for disconnecting said tone, for causing the transmission of order tones to said first ofiice and the subsequent connection of said telephone set into a talking connection with said first ofilce over said trunk, and means operable by a second operation of said key for disconnecting said position equipment from said trunk.

4. In a telephone exchange system, first offices, a second ofiice, trunks for trunking calls from a first oilice to said second oifice, an operators position equipment at said second Iofiice having a telephone set and a key, means operable upon the seizure of a trunk at a first ofiice for associating said operators position equipment with said trunk, means operative upon the association of said trunk with said position equipment 'for transmitting a tone to said operator's telephone set as a. call waiting signal, a relay operable upon the first operation of said key for discontinuing said tone, means controlled by said relay for sequentially causing the transmission of order tones to said first ofiice and connecting said telephone set into a talking connection'with said first ofiice over said trunk circuit, a second relay operable upon the release of said key, and means controlled by said'second relay and operable by a second operation of said key for disconnecting said position equipment from said trunk.

5. In a telephone exchange system, first offices, a second ofiice, trunks for trunking calls from a first oifice to said second oflice, an operators position equipment at said second office having a telephone set and a key, means operable upon the seizure of a trunk at a first ofiice for associating said operators equipment with said trunk, a source of tone current, a relay operative upon the association of said trunk with said position equipment for connecting said source of tone current to said telephone set as a call waiting signal, a second relay operable upon the first operation of said key for releasing said first relay to disconnect said source of tone current from said telephone set and to operate means for first causing the transmission of order tones from said source to said first ofiice and for then connecting said telephone set into atalking connection with said first ofiice over said trunk, a third relay operable upon the release of said key and means controlled by saidlatter relay and operable by a second operation of said key for disconnecting said position equipment from said trunk. 1

6. In a telephone exchange system, first oifices, a secondofiice, trunks for trunking calls from a first officeto said second ofiice, an operator's position equipment at said second ofiice associable with said trunks, said equipment including a telephone set and a key, means operable upon the seizure of more than one'of said trunks at a first ofilce for associating said operators position equipment with afirst one of said trunks, means operable by a first operation of said key. for connecting said telephone set into a talking connec tion with said first ofiice over said first trunk, and means operable by a second operation of said key for entirely disassociating said position equip ment from said first one of said'trunks and for connecting said telephone set into a talking con.- nection with another of said seized trunks.

7. In'a telephone exchange system, first ofiices, a second office, trunks for trunking calls from a first ofiice to said second ofiice, an operators position equipment at said second office associable with said trunks, said equipment including a tele-', phone set and a key, -means operable uponithe' seizure of more than one of said trunks atv a first ofiice for associating said operators equipment with a first one of said trunks, means operative upon the association of said first trunk with said position equipment for transmitting a tone signal to said operators telephone set, means operable by a first operation of said key for discontinuing said tone signal and for connecting said telephone set into a talking connection with saidfirst office over said first trunk, andimeans operable by a second operation of said key for disassociating said position equipment from said first trunk and for connecting said telephone set into a talking connection with another of saidseized trunks without transmitting a tone signal to said operators telephone set.

8. In a telephone exchange system, first offices, a second 'oifice, trunks for trunking calls from a first ofiice to said second office, an operators position equipment at said second ofiice associable with said trunks, said equipment including a telephone set and a key, means operable'upon the seizure of more than one of said trunks at a first ofiice for associating, said operators equipment with a first one of said trunks, means operative upon the association of said first trunk with said position equipment for transmitting a tone signal to said operators' telephone set, means operable by a first operation of said key for discontinuing said tone signal, for causing the transmission of order tones to said first ofice and the subsequent connection of said telephone set into a talking connection with said firstorfice over said first trunk, and means operable by a second operation of said key fordisassociating said position equipment from said first trunk and for causing the transmission of order tones to said first office over another of. said seized trunks and for subsequently connecting said telephone set into a talking connection with said first office over said other trunk. v

9. In a telephone exchange system, first ofiices, a second ofiice, trunks for trunking calls from a first ofiice to said second ofilce, an operatorsposition equipment at said second office associable with said trunks, said equipment including a telephone set and a key, means operable upon the seizure of more than one of said trunks at a first able by each following operation of said key for entirelydisassociating said position equipment from the trunk with which it is associated and for connecting said telephone set into a talking connection with another of said seized trunks.

- 10. In a telephone exchange system, first of,-

fices, a second ofiice, trunks for trunking calls from a first oifice to said second ofiice, an operator's position equipment atsaid second office associable with said trunks, said equipment including a telephone set, a key and a source of tone current, means operable upon the seizure of more than one of said trunks at a first office for associating said operators equipment with a first one of said trunks, means operable by a first operation of said key for first transmitting order tones from said source to said first office over said first trunk and for then connecting said telephone set into a talking connection therewith, and means operable by each following operation of said key for disassociating said position equipment from the trunk with which it is associated and for then sequentially causing the transmission of order tones from said source over another of said seized trunks and connecting said telephone set into a talking connection therewith.

11. In a telephone exchange system, first offices, a second office, trunks for trunking calls from a first office to said second office, an operators position equipment at said second office associable with said trunks, said equipment including a telephone set, a key and a source of tone current, means operable upon the seizure of more than one of said trunks at a first office for associating said operato-rs equipment with a first one of said trunks, a relay operable upon the association of said first trunk with said position equipment for connecting said source of tone current to said telephone set, a second relay operable upon the first operation of said key for releasing said first relay to disconnect said source of tone current from said telephone set and to operate means for first causing the transmission of order tones from said source to said first office over said first trunk and for then connecting said telephone set into a talking connection therewith, a third relay operable upon the release of said key, and means controlled by said latter relay and operable by each following operation of said key for disassociating said position equipment from the trunk with which it is associated and for then sequentially causing the transmission of order tones from said source over another of said seized trunks and connecting said telephone set into a talking connection therewith.

WALTER B. STRICKLER. 

